Several different integrated circuit technologies are available to circuit and system designers in which to realize their designs. These technologies include, for example, bipolar transistor-transistor logic (TTL), complementary metal oxide semiconductor (CMOS), bipolar-CMOS (Bi-CMOS), gallium arsenide (GaAs), and others. As would be expected, integrated circuits based on differing technologies are often required to operate within a single system and hence must communicate one with another. A common problem that must be dealt with is the differing voltage and logic levels associated with the differing technologies or between differing circuit families within a single technology. This problem is sometimes further exacerbated by supply voltage levels which may vary significantly, not only between different technologies but even amongst circuits of like technologies.
Thresholds of the input circuits need to be compatible with the input signal levels from the external source.
Patent application Ser. No. 08/769,976, A LOW VOLTAGE INPUT BUFFER FOR ASYMMETRICAL LOGIC SIGNALS filed Dec. 19, 1996, of common assignee herewith discloses an input buffer circuit for responding to logic signals centered around a known fixed threshold which respond to input signal levels from an external circuit and translate these into needed logic levels for the internal circuits. What is needed is an integrated circuit which responds to a multiplicity of logic thresholds.